Abstract
Relaxor ferroelectrics (RF) are outstanding materials owing to their extraordinary dielectric, electromechanical, and electro-optical properties. Although their massive applications, they remain to be one of the most puzzling solid-state materials because understanding their structural local order and relaxation dynamics is being a long-term challenge in materials science. The so-called Vogel-Fulcher-Tamman (VFT) relation has been extensively used to parameterize the relaxation dynamics in RF, although no microscopic description has been firmly established for such empirical relation. Here, we show that VFT equation is not always a proper approach for describing the dielectric relaxation in RF. Based on the Adam-Gibbs model and the Grüneisen temperature index, a more general equation to disentangle the relaxation kinetic is proposed. This approach allows to a new formulation for the configurational entropy leading to a local structural heterogeneity related order parameter for RF. A new pathway to disentangle relaxation phenomena in other relaxor ferroics could have opened.
Highlights
Materials are usually ordered at low temperatures whereas they show disordered states at high temperatures
Model-free route (MFR) has been recently extended for studying the low-temperature dielectric relaxations of normal ferroelectrics[31], but this approach has never applied before to study the dynamic of Relaxor ferroelectrics (RF)
Generalized VFT equations with fractional exponent have been previously proposed for describing dielectric relaxation of SCL39,40
Summary
Materials are usually ordered at low temperatures (e.g., crystals) whereas they show disordered states at high temperatures (e.g., liquids). Www.nature.com/scientificreports disordered systems where the arrangement of different ions on equivalent crystallographic sites (A or B) is partially or fully disordered[7]. The emergence of the PNRs is related to disordered chemical inhomogeneities that unavoidably exist in these materials such as Pb2+ or O2− vacancies, antisite ions (e.g. Nb/Mg arrangement in PMN), and so on[16]. The quenching of these disordered chemical inhomogeneities leads to the development of the disordered state being the time-response to switch their polarization vector to follow the applied external stimuli (usually applied electric fields) defined as the relaxation time (τ)
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